Instruments for detecting specific gases or liquids in the adjacent environment have varied uses which include, among many others, the detection of toxic or explosive gases in the atmosphere, monitoring fluid flow constituents in industrial processes and detection of ground water contamination. There are many different known instruments for such purposes which variously respond to electrical, chemical or optical effects induced by the presence of the gas or liquid.
Many such instruments, for example, sense changes in electrical conductivity in a medium that result from the presence of the fluid. Others contain some substance that reacts chemically with the fluid to produce changes that are visible or otherwise detectable. Still others respond to changes of light conductivity or operate on the basis of X-ray, mass or optical spectrometry.
Each general type of fluid detector tends to have characteristics which make it suitable for some uses and inappropriate for others. Many are very costly and/or bulky and may require highly skilled operators. Some are inherently fragile and some are extremely sensitive to contamination. Detectors which depends on electrical effects to generate and/or transmit the desired data are prone to malfunction from electromagnetic interference. Detectors which require electrical conductors for signal transmission are also unsuitable for use in high voltage regions in the absence of substantial structural complications. Electronic detectors can also be hazardous if used for the detection of inflamable or explosive fluids because of the risk of ignition.
It would be advantageous if a fluid detector were available which can provide sensitive and reliable response while having a compact and inexpensive construction when that is desirable and which can be operated in diverse environments without complications. Such a detector should be immune to electromagnetic interference and should be capable of transmitting data over long distances without structural complication.
Insofar as I am aware, fiber optic technology has not been extensively used in gas or liquid detectors except possibly for transmitting data that has been generated by one of the conventional fluid detectors discussed above. One known technique which uses fiber optic elements in conjunction with the detection of gases relies on the fact that certain gases strongly absorb light of certain specific wavelengths. The presence of such gases in a region adjacent one end of a fiber optic element is sensed by directing light into the opposite end of the element and detecting variations of the intensity of the specific wavelengths after passage of the light through the region. The fiber optic element in such a system is essentially confined to the role of transmitting light to a detection site which is outside the fiber optic element. The apparatus does not operate on the basis of direct interaction between the detected fluid and the fiber itself.
The present invention is directed to overcoming one or more of the problems discussed above.